Method for angular orientation of hollow bodies in a plant for manufacturing containers

ABSTRACT

A method for regulation of the angular position of hollow bodies in an installation for production of containers. The hollow bodies are moved by individual support members each of which is equipped with means for causing the hollow body to turn about its axis. The method includes a first step of measuring an angular offset of at least one particular hollow body relative to a reference angular position in a measurement zone. The method also includes a second step of compensating of the angular position of the subsequent hollow bodies in a compensation zone upstream of said measurement zone as a function of the angular offset measured for the at least one particular hollow body.

TECHNICAL FIELD OF THE INVENTION

The invention concerns a method for regulation of the angular positionof hollow bodies in an installation for production of containers byforming thermoplastic material preforms in which the hollow bodies aremoved in single file along a production itinerary by individual supportmembers each of which is equipped with means for causing the preform toturn about its axis, the method including a first step of measuring anangular offset of at least one particular preform relative to areference angular position in a particular measurement zone of theproduction itinerary.

TECHNICAL BACKGROUND

In the remainder of the description and in the claims the term “hollowbody” will interchangeably designate a preform or a container.

It is known to produce thermoplastic material and in particularpolyethylene terephthalate (PET) containers by forming, and inparticular by blowing-stretching, preforms the body of which is heatedbeforehand. The hollow bodies have a neck that is already molded to itsfinal shape and is therefore intended to remain unchanged during theproduction of the container.

In many cases the preforms are produced by injection molding at a firstlocation and are blow molded to the final shape of the container at asecond location in a specific production installation.

This kind of technology enables the blow molding operation to be carriedout as close as possible to the bottling location, the injection moldingoperation having been effected anywhere. In fact, it is relatively easyand relatively inexpensive to transport small preforms whereastransporting containers after forming has the disadvantage of low costeffectiveness because of their very large volume.

The series production of such containers is carried out in a containerproduction installation in which the hollow bodies follow a productionitinerary in single file.

To enable it to be formed, the body of the preform is heated above aglass transition temperature enabling the wall of the body to berendered malleable. In contrast, the neck is maintained at a temperaturebelow the glass transition temperature to prevent deformation thereof.To this end the production installation includes a heating station thatenables the body of the preforms to be heated to the requiredtemperature to carry out the forming step.

The heated preforms are then routed to a forming station of theproduction installation. The forming station is equipped with numerousforming substations each of which includes a mold and a device forinjection of a forming fluid under pressure into a preform received inthe mold. The large number of forming substations enables production ofthe containers at a high rate, for example greater than or equal to50,000 bottles per hour. The forming substations are for example carriedby a carousel that turns so that the preforms are blown one after theother at a high rate during their movement between an introduction pointcorresponding to the introduction of the preforms into an associatedmold and an extraction from the mold point corresponding to the ejectionof the formed containers out of the molds.

The containers obtained in this way are received when they exit the moldby holding means of a transfer wheel in order for them to be routed insingle file to another device, for example via a conveyor. The nextstation is for example a filling station or a labeling station.

The stations themselves are generally equipped with container transportdevices such as carousels. The production installation is also equippedwith transport devices between two stations.

It is sometimes necessary to modify the angular orientation of thehollow bodies during their movement through the production installation.

This kind of modification of the angular orientation is necessary forexample if the containers to be obtained have at least one section thatit not axisymmetrical relative to the axis of the neck. To obtain thiskind of non-axisymmetrical container the preforms are generallypreferentially heated in certain parts, by a process generally known as“preferential heating”. The preforms are then received in the molds witha particular orientation about their main axis to cause the heatingprofile of the bodies to correspond to the imprint of thenon-axisymmetrical container to be obtained.

To guarantee that the orientation of the preforms remains under controlbetween their entry into the heating station and their exit from theforming station the transport devices include individual support membersthat are designed to hold the preform in such a manner as to preventslippage between the preform and its individual support member, inparticular in order to prevent any uncontrolled rotation of the preformabout its principal axis.

It is known to equip the neck of the preforms with an angular markerthat enables monitoring and correction of their angular orientationabout the axis of the neck relative to a support. The neck retaining itsshape during the process of production of the container, this angularmarker remains usable to enable orientation of the preform and of thefinished container about the axis of its neck throughout the productionprocess and during subsequent treatments.

This angular marker enables the angular orientation of the preform or ofthe container relative to each individual support member to bedetermined and possibly the angular orientation of the preform or of theindividual support member to be modified to bring the angular markerinto a particular reference position relative to the individual supportmember.

In a non-limiting manner, this kind of angular marker may be producedwhen injection molding the preform in the form of an angular marker inrelief. It is for example a notch produced in a flange of the neck or alug produced in a groove situated above the flange. Thus the preform isalready equipped with its own angular marker before feeding thecontainer production installation.

This kind of preform is angularly indexed a first time when it is takenup by the heating station in order to cause the heating profile tocorrespond to the angular marker with which the preform is alreadyequipped.

However, when the preform is transferred from one transport device tothe next transport device, it can happen that the preform undergoesuncontrolled pivoting about its principal axis relative to theindividual support member. Likewise, when the preform is deposited in amold of the forming station, it remains free to turn about its principalaxis during a very short time between the moment at which it is releasedinto the mold by the directly upstream transport device and the momentat which it is immobilized by a nozzle of the molding substation.

To alleviate this problem, the orientation of each preform is verifiedin a measurement zone of the production itinerary thereof and if anangular offset is detected relative to a reference angular position theorientation of said preform is corrected during a correction operationin a correction zone of the production itinerary downstream of themeasurement zone, for example when it is taken up by the formingstation, so that the heating profile of said preform corresponds exactlyto the imprint of the mold.

In a known variant the correction is effected without measurement byturning the preform until a sensor detects that the angular markerequipping the neck is in the reference angular position.

If the preform is taken up in the heating station with an angularindexing error, its heating profile no longer coincides with its angularmarker. This error persists in the mold, since the orientation of thepreform in the mold is determined thanks to its angular marker. It istherefore necessary to verify the orientation of the preform in ameasurement zone at the start of a heating path and then to correct theorientation of said preform downstream of the measurement zone so thatits heating profile corresponds exactly to the position of the angularmarker.

However each operation of correction of the position of the preform hasa duration proportional to the value of the angular offset to becorrected in the correction zone. The result of this is that theproduction rate is limited by the correction operation.

Moreover, it happens that the heating profile is slightly offsetrelative to the position of the angular marker. This may be caused byslippage of the preforms between the first measurement zone and beingtaken up by the heating station.

SUMMARY OF THE INVENTION

The invention proposes a method of regulation of the angular position ofhollow bodies in an installation for production of containers by formingthermoplastic material preforms in which the hollow bodies are moved insingle file along a production itinerary by individual support members,each of which is equipped with means for causing the hollow body to turnabout its axis, the method including a first step of measuring anangular offset of at least one particular hollow body relative to areference angular position in a particular measurement zone of theproduction itinerary,

characterized in that it includes a second step of compensation of theangular position of the subsequent hollow bodies in a compensation zoneupstream of said measurement zone during which the angular orientationof the subsequent hollow bodies is modified by an updated compensationangle that is a function of the angular offset measured for the at leastone particular hollow body in the first step and that is a function of acurrent compensation angle in such a manner as to reduce the angularoffset of the hollow bodies in said measurement zone.

In accordance with other features of the invention:

-   -   the value of the current compensation angle is modified in the        second step if the mean of the angular offsets of each hollow        body of a string of at least two consecutive particular hollow        bodies measured in the first detection step has an absolute        value above a particular threshold;    -   in the second compensation step, the updated compensation angle        is calculated by subtracting the mean of the angular offsets of        the string of particular preforms from the current compensation        angle;    -   the method is reiterated cyclically, the current compensation        angle being formed by the updated compensation angle of the        preceding iteration;    -   during the first iteration, the current compensation angle is        initialized to 0°;    -   the installation includes a heating station that is equipped        with a transport device provided with support means, termed        turntables, each of which enables individual transportation of a        preform along a heating path forming a section of the production        itinerary and each of which enables the preform to be caused to        turn about its axis, the compensation zone being arranged on the        heating path where the preforms are supported by a turntable,        the compensation of the angular position of the preforms being        achieved by rotation of each turntable by the updated        compensation angle in the compensation zone;    -   the transport device includes a chain of turntables movement of        which is guided by two guide wheels, the compensation zone being        situated in a run of the chain that meshes with one of the guide        wheels;    -   the compensation zone is situated in a run of the chain that        meshes with a guide wheel downstream of a take-up point at which        the preforms are transferred from an upstream transport device        and before the beginning of the heating of the preform;    -   the measurement zone is situated in the heating station in a run        of the chain that meshes with a guide wheel upstream of a        transfer point at which the preforms are transferred to a        downstream transport device in the direction of a forming        station and after the heating of the preform has been finished;    -   the production installation includes a forming station in which        each hollow body is moved along a forming path forming a section        of the production itinerary, each preform undergoing an        operation of forming it into a final container along the forming        path;    -   the compensation zone is situated in a run of the chain that        meshes with a guide wheel upstream of a transfer point at which        the preforms are transferred to a downstream transport device in        the direction of a forming station and after the heating of the        preform has finished;    -   the measurement zone is situated in the forming station        downstream of the heating station before the forming operation        is begun;    -   the compensation zone is situated along the forming path before        the forming operation is begun;    -   the measurement zone is situated in the forming station along        the forming path after the forming operation has been finished.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will become apparentduring a reading of the following detailed description to understandwhich refer to the appended drawings in which:

FIG. 1 is a view from above that represents schematically aninstallation for production of containers from preforms;

FIG. 2 is a side view that represents a preform intended to be taken upby the installation from FIG. 1 ;

FIG. 3 is a view from above to a larger scale that schematicallyrepresents a heating station that is part of the production installationfrom FIG. 1 ;

FIG. 4 is a view in section taken along the section line 4-4 in FIG. 3that represents a portion of a chain for transporting preforms throughthe heating station;

FIG. 5 is a view in section taken along the section line 5-5 in FIG. 3that represents a preform carried by a turntable that is interengagedwith a device for orienting the turntable;

FIG. 6 is a view in section taken along the section line 6-6 in FIG. 5that represents a crankpin of a turntable engaged between two fingers ofthe orientation device;

FIG. 7 is a view in axial section that represents a forming substationequipping a forming station of the installation from FIG. 1 and in amold of which a preform is installed, a nozzle of the forming substationoccupying a retracted extreme position;

FIG. 8 is a view similar to that of FIG. 7 that represents the nozzle ina working extreme position in which it is able to inject a forming fluidinto the preform;

FIG. 9 is a view similar to that of FIG. 7 in which the nozzle occupiesan orientation intermediate position, a member for driving the nozzlebeing interengaged with the preform to enable driving thereof inrotation;

FIG. 10 is a view in elevation that represents a carousel of the formingstation that carries a plurality of forming substations, the formingstations being equipped with two imaging devices;

FIG. 11 is a perspective view that represents the neck of a hollow bodyincluding four angular markers;

FIG. 12 is a view from above that represents the neck of a preformduring its passage at a target point at which one of the imaging devicesof the installation is aimed, the preform being oriented in accordancewith a first current angular orientation;

FIG. 13 is a view similar to that of FIG. 12 that represents anotherpreform oriented in accordance with a second current angularorientation;

FIG. 14 represents an image of the neck of the preform from FIG. 12captured from the side by the imaging device from FIG. 12 ;

FIG. 15 represents an image of the neck of the preform from FIG. 13captured from the side by the imaging device from said FIG. 13 ;

FIG. 16 represents a diagram representing on the abscissa axis theangular offset measured between the current angular position of a hollowbody and a reference angular position and representing on the ordinateaxis the number of hollow bodies having said angular offset, a curverepresenting the distribution of the angular offsets for a string ofseveral hollow bodies, the mean of the angular offsets being offsetrelative to the value 0°;

FIG. 17 represents a diagram similar to that from FIG. 16 in which themean of the angular offsets is equal to 0°;

FIG. 18 is a block schematic that represents the compensation methodcarried out in accordance with the teachings of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the remainder of the description elements having an identicalstructure or analogous functions will be designated by the samereference.

There has been represented in FIG. 1 an installation 10 for productionof containers 12B from preforms 12A. Hereinafter and in the claims thepreforms 12A and the containers 12B will be designated interchangeablyby the generic term hollow body 12. In the remainder of the descriptionthe terms “upstream” and “downstream” will be used with reference to thedirection of movement of the hollow bodies 12 in single file along aproduction itinerary 13.

The invention is intended to be applied when the production installation10 produces containers 12B.

Here the production itinerary 13 extends in a globally horizontal planewhile the hollow bodies 12 have a principal axis “Z1” that extendsvertically, that is to say orthogonally to the horizontal plane.

The hollow bodies 12 are moved in a continuous manner through theproduction installation 10 along the production itinerary 13 that isindicated in bold line in FIG. 1 . The hollow bodies 12 are moved byvarious transport devices, some of which will be described in detailhereinafter, that include individual support members for each hollowbody 12. The transport devices are arranged as a chain in such a mannerthat each hollow body 12 is able to be transferred from one transportdevice to another to continue the production itinerary 13 while beingcontinuously held by at least one individual support member.

In the remainder of the description angular values are expressed indegrees.

There has been schematically represented in FIG. 1 the installation 10for series production of thermoplastic material containers 12B frompreforms 12A. In a non-limiting manner here the containers 12B arebottles. Here the thermoplastic material is polyethylene terephthalate,designated hereinafter by its acronym “PET”.

There has been represented in FIG. 2 an example of a hollow body 12,here in the form of a preform 12A. A preform 12A of this kind is made ofa thermoplastic material, here of polyethylene terephthalate (PET). Thepreform 12A is globally axisymmetrical and has a principal axis “Z1”represented vertically in FIG. 2 . It includes a body 14 having a closedaxial end, represented at the bottom in FIG. 2 . The opposite end of thebody 14, represented at the top in FIG. 2 , leads into an open neck 16.The neck 16 has a tubular shape the principal axis of which defines theprincipal axis “Z1” of the preform 12A.

The general shape of the body 14 is that of an axisymmetrical elongatetube extending along the principal axis “Z1”. The neck 16 of the preformalso includes an annular flange 18 that projects radially. The neck 16,including the flange 18, is delimited on the outside by an external face17.

A portion of the external face 17 of the neck 16 has a globallycylindrical shape. It generally includes means for fixing a cap, forexample a thread or a groove for elastically nesting with the cap.Referring to FIG. 1 , the production installation 10 includes a station20 for heating the preforms 12A. By way of non-limiting example aheating station 20 includes heating members 22 emitting heatingelectromagnetic radiation, for example infrared radiation, such ashalogen lamps or laser emitters. Reflectors (not represented) aregenerally arranged facing each heating member 22 on either side of theheating path to enable reflection of the heating radiation in thedirection of the preforms.

As will be explained in more detail hereinafter, the heating station 20includes a device 24 for transporting hollow bodies 12 in the form ofpreforms 12A that causes them to move along the heating members 22. Thedirection of movement of the preforms 12A is indicated by the arrows inFIG. 1 .

At the exit from the heating station 20 the body 14 of the preforms 12Ais rendered malleable by heating above a glass transition temperaturewhile the neck 16 is maintained at a temperature sufficiently low toretain its original shape.

The production installation 10 also includes a station 26 for formingthe heated preforms 12A into finished containers 12B. The formingstation 26 is downstream of the heating station 20 with reference to theflow of hollow bodies 12 along the production itinerary 13.

Here the forming station 26 includes a carousel 28 carrying a pluralityof forming substations 30. The carousel 28 is mounted to rotate about acentral axis “Z2”. Each forming substation 30 can therefore be movedaround the axis “Z2” of the carousel 28 between a point 32 forintroduction of the hot preforms 12A and a point 34 for extraction ofthe finished containers 12B from the mold before resuming a new cycle.The forming substations 30 will be described in more detail hereinafter.

Referring to FIG. 3 , the heating station 20 has been represented inmore detail. The transport device 24 enables the preforms 12A to bemoved in single file along a heating path 36 that is indicated inthicker line in FIG. 3 . The heating path 36 forms a section of theproduction itinerary 13.

The transport device 24 includes a string of individual support members37 referred to hereinafter as “turntables 38”, each of which is able tosupport an individual preform 12A.

As represented in FIG. 4 , this kind of turntable 38 includes a mandrel40 that is temporarily fastened to the neck 16 of a preform 12A, for thetime taken to transport it along the heating path 36. The preform 12A isin particular immobilized against rotation about its principal axis “Z1”relative to the mandrel 40.

The mandrel 40 is for example forcibly driven into the neck 16 of thepreform 12A which is therefore temporarily fastened to the mandrel 40 byfriction. The necessary friction is for example provided by an elastomermaterial ring (not represented) disposed in a groove around the mandrel40.

The mandrel 40 is fixed to the lower end of a shaft 42 with axis “Z3”coaxial with the principal axis “Z1” of the preform 12A it carries. Theshaft 42 is received in a guide bearing 44 of a link 46 of the transportdevice 24. The shaft 42 is more particularly mounted to rotate in theguide bearing 44 about its principal axis “Z3”. That rotationadvantageously makes it possible to be able to expose the whole of thebody 14 of the preform 12A to the heating radiation emitted by theheating members 22 in a controlled manner.

Moreover, here the shaft 42 is mounted to slide vertically relative tothe link 46. The link 46 includes a lower sleeve 48 that has an annularlower end face 50 termed the “stripping face 50”. The shaft 42 istherefore mounted to slide between the active lower position, asrepresented on the left in FIG. 4 , in which the mandrel 40 can befastened to the neck 16 of the preform 12A, and an inactive upperposition, as represented on the right in FIG. 4 , in which the mandrel40 is retracted into the sleeve 48, above the lower end face 50, toenable the mandrel 40 to be unfastened from the neck 16 of the preform12A, which remains immobilized outside the sleeve 48 by abutting againstthe stripping face 50.

In a non-limiting manner, here the mandrel 40 is driven toward itsinactive position by means of a cam device (not represented) and urgedtoward its active position by an elastic member 52, here a spring,disposed vertically between the mandrel 40 and the link 46.

Here the rotation of the mandrel 40 about the principal axis “Z1” of thepreform 12A is driven by means of pinion 54 that here is arranged at anupper end of the shaft 42, above the link 46. The pinion 54 is intendedto cooperate with a rack 56 that is disposed over at least a section ofthe heating path 36.

In a variant of the invention that is not represented the rotation ofthe mandrel 40 is driven by an individual electric motor on the link 46.This rotation is then controlled by an electronic control unit. Hereeach link 46 carries a single turntable 38. The links 46 are assembledin a manner articulated to one another as a chain around the principalaxis “Z3” by means of a hinge 58. Thus the links 46 are assembled toform the closed chain 37.

The chain 37 is meshed around a first guide wheel 60 and a second guidewheel 62 each of which is mounted to rotate about a vertical axis “Z4,Z5”. At least one of the guide wheels 60, 62 is driven, here clockwise,by at least one motor (not represented) to enable driving of the chain37.

Here each turntable 38 is moved continuously, that is to say withoutinterruption, along a closed circuit. A usable section of said closedcircuit, represented in thicker line in FIG. 3 , forms the heating path36 along which each turntable 38 is intended to carry a preform 12A. Anempty section, which the turntables 38 travel empty, completes thecircuit.

On the heating path 36 each turntable 38 transports a preform 12A from apoint 64 where the preforms 12A are taken up to a point 66 at which thepreforms 12A are transferred to the forming station 26. The take-uppoint 64 and the transfer point 66 are at the periphery of the firstguide wheel 60.

The preforms 12A are fed one by one to the take-up point 64 by anupstream transport device, for example by means of a notched wheel 68.At the take-up point 64 each mandrel 40 is inserted in the neck 16 of apreform 12A fed by the notched wheel 68. The notched wheel 68 isprovided with notches 69 at its periphery each of which is intended tosupport one preform 12A.

On leaving the heating path 36 the hot preforms 12A are transferred to adownstream transport device, for example a transfer wheel 70 that hereis equipped with clamps 72 that are intended to seize each preform 12Aby its neck 16. The turntables 38 are then driven toward their inactiveposition by means of a driving fork 74 which can be seen in FIG. 4 andwhich here is carried by the first guide wheel 60. Each driving fork 74is mounted to slide vertically. The sliding of each driving fork 74 isdriven for example by a cam (not represented). The first guide wheel 60more particularly includes a plurality of forks 74 at its periphery. Agroove 76 on each turntable 38 is intended to be interengaged with afork 74 to drive sliding thereof, as illustrated in FIG. 4 .

In the empty section the empty turntables 38 move from the transferpoint 66 to the take-up point 64. The empty section is on a run “B1” ofthe chain 37 that meshes around the first guide wheel 60.

The heating path 36 includes at least one active section along which thebody 14 of the preform 12A is exposed directly to the heating radiationfrom the heating members 22, symbolized by arrows shaped like lightningbolts in FIG. 3 , and at least one passage section along which the body14 of the preform 12A is not exposed to the heating radiation from theheating members 22.

In the example illustrated in FIG. 3 the heating station 20 includes anupstream active section “H1”, sometimes termed the “penetration”section, and a downstream active section “H2”, sometimes termed the“distribution” section, that are formed by two rectilinear runs of thetransport chain 37 tensioned between the two guide wheels 60, 62. Theheating members 22 are arranged along these two active sections “H1, H2”in such a manner that the bodies 14 of the preforms 12A traveling alongthese active sections “H1, H2” are exposed to the heating radiation. Thepreforms 12A are generally driven in rotation about their principal axis“Z1” when they travel through the active heating sections “H1, H2” toenable heating of the body 14 of the preforms 12A over all theircircumference. To this end each section “H1, H2” includes a rack 56 fordriving the turntables 38 in rotation.

Here the heating path 36 includes three passive sections along which thebody 14 of the preforms 12A is not exposed to the heating radiationemitted by the heating members 22. Here there is no heating member inthe passive sections.

An upstream first passive section “P1” is arranged between the take-uppoint 64 and the upstream active section “H1”. The upstream firstpassive section “P1” is therefore situated on a run of the chain 37 thatmeshes with the first guide wheel 60.

An intermediate second passive section “P2” is interleaved between theupstream active section “H1” and the downstream active section “H2”. Theintermediate second passive section “P2” more particularly has acircular arc shape because it extends over a run of the chain 37 that ismeshed around the second guide wheel 62.

The downstream third passive section “P3” is arranged between thedownstream end of the downstream active section “H2” and the transferpoint 66. The downstream third passive section “P3” is thereforesituated on a run of the chain 37 that meshes with the first guide wheel60.

Protection members (not represented) are provided to protect the necks16 of the preforms 12A from the heating radiation in order to maintainthe necks 16 at a temperature below the glass transition temperature.

The orientation of each turntable 38 is controlled all the way along theheating path 36. In the embodiment represented in the figures,especially in FIG. 4 , each turntable 38 here includes a crank pin 78that is arranged in an eccentric manner relative to the rotation axis“Z3”. The crank pin 78 is intended to enable correct orientation of theturntable 38 on passing from each passive section “P1, P2, P3” to thenext active section “H1, H2” between a set 80 of two convergent rampsdisposed along the path of the turntable 38. Thus the crank pin 78 isautomatically positioned toward the upstream side relative to thedirection of movement of the turntables 38. At the exit from this set 80of convergent ramps the pinions 54 mesh directly with the rack 56 sothat the orientation of the turntables 38 can be readily deduced fromits position along the heating path 36 as long as the pinion 54 isinterengaged with the rack 56.

When the turntables 38 arrive at the level of the first guide wheel 60the crank pin 78 is received between two fingers 82 of an orientationdevice 84 that is carried by the first guide wheel 60. The orientationdevice 84 also includes a motor 86 that enables the fingers 82 to becaused to turn about the axis “Z3” relative to the first guide wheel 60so as to be able to orient the turntables 38 around their axes “Z3”, asillustrated in FIGS. 5 and 6 . The first guide wheel 60 thereforeincludes a plurality of orientation devices 84 at its periphery in sucha manner that each turntable 38 is taken in charge by an orientationdevice 84 on the meshing run.

In a variant of the invention that is not represented the racks and/orthe orientation devices may be replaced by an individual motor fordriving in rotation the turntable 38 that is carried by each link 46.

The parameter settings of each heating member 22 can be controlled so asto heat some portions of the body 14 of the preform 12A either more orless. The parameters that can be adjusted comprise for example theposition of each heating member 22 relative to the heating path 36and/or the power of the radiation emitted by each heating member 22and/or the opacity of the reflectors facing some heating elements 22.The parameters are for example controlled automatically by an electroniccontrol unit. Accordingly, by simultaneously controlling the orientationof the turntable 38 and the power of the heating radiation at everypoint of the heating path 36 it is possible to heat the body 14 of thepreform 12A in accordance with a so-called “preferential” heatingprofile that thereafter makes it possible to confer a non-axisymmetricalshape on the finished container 12B during the forming operation.

The heated preform 12A is then sent to a forming substation 30 of theforming station 26 by means of the transfer wheel 70 which transfers thepreforms to another, directly downstream transport device which here isformed by a second transfer wheel 87 itself equipped with clamps 89 forindividually grasping each preform 12A.

In a variant of the invention that is not represented a single transferwheel transports the preforms between the heating station and theforming station.

As explained above, the forming substations 30 are carried by a rotarycarousel 28. In production the carousel 28 turns continuously. Ittherefore enables movement of the preforms 12A/containers 12B along aforming path that forms a section of the production itinerary 13.

A forming substation 30 of this kind equipping the forming station 26 isshown in more detail in FIG. 7 . In known manner the forming substation30 includes a forming mold 88 that is generally made up of two or threeparts mobile relative to one another to enable a clamp 89 of thedirectly upstream transport device, here the second transfer wheel 87,to introduce the hot preform 12A into a molding cavity 90 formed insidethis mold 88 and to enable the container 12B to be extracted from themold 88 after the forming operation. When the parts of the mold 88 areassembled the mold 88 has a globally plane upper face 92 through whichpasses a through-orifice 94 with vertical axis “Z6” that opensvertically into the molding cavity 90. Thus each mold 88 forms anindividual support member for a preform 12A enabling it to betransported along the forming path.

The forming station 30 also includes a device 96 for injection of aforming fluid, for example air, under pressure. The injection device 96includes a nozzle 98 that is arranged vertically above the mold 88 andis intended to be caused to slide vertically downward on the axis “Z6”of the passage orifice 94 facing the neck 16 of the preform 12A in orderto inject into it air under pressure and thus to force the material ofthe body 14 of the preform 12A to deform and to espouse the shape of themolding cavity 90.

In accordance with a known design of the injection device 96, the nozzle98 has a tubular shape. It is mobile vertically in a fixednozzle-carrier block 100 of the forming substations 30. The nozzle 98has passing through it along the axis “Z6” a stretcher rod 102 that isdriven vertically by a cylinder, an electric motor or a cam/rollerdevice (none of which is represented) to be engaged in the preform 12Aand to guide the vertical deformation of the latter during forming, inparticular by blowing.

In the example illustrated the forming substation 30 is equipped with abell nozzle 98 comparable to that described in French patentFR-2.764.544. Thus the nozzle 98 is provided at its lower end with abell-shaped part 104 that is open at its lower end so as to come to bearin sealed manner on the upper face 92 of the mold 88 around the neck 16of the preform 12A, as represented in FIG. 8 , and not to bear on thelatter. Once the bell 104 is pressing on the mold 88 the nozzle 98 is influid-tight communication with the interior of the preform 12A in orderto inject gas under pressure into it.

In a variant that is not represented the lower end of the nozzle 98comes into fluid-tight contact with the neck 16 of the preform 12A toinject gas under pressure.

The nozzle 98 and therefore the bell 104 can be positioned verticallybetween two extreme positions.

In FIG. 7 the nozzle 98 is in a first extreme position termed the“retracted extreme position” in which it enables loading of the preform12A into the mold 88 and then extraction of the container 12B onceformed. In this retracted extreme position the bell 104 is spacedvertically above the upper face 92 of the mold 88.

In FIG. 8 the nozzle 98 is illustrated in a second extreme positiontermed the “working extreme position” in which the bell 104 bears influid-tight manner on the upper face 92 of the mold 88, encompassing thepassage orifice 94 and the neck 16.

The movements of the nozzle 98 between its two extreme positions may bedriven in various ways. The sliding of the nozzle 98 is for exampledriven by means of a linear electric motor 105. In a variant of theinvention that is not represented the sliding of the nozzle is drivenwith the aid of a multistage pneumatic actuator system.

The nozzle 98 includes a drive member 114 that enables the preform 12Ato be held firmly in position when installed in the mold 88 during theforming operation, in particular when the forming fluid under pressureis introduced into the preform 12A. The drive member 114 is spacedvertically from the preform 12A when the nozzle 98 occupies itsretracted extreme position. The drive member 114 is intended to comeinto contact with the installed preform 12A when the nozzle 98 is movedvertically from its retracted extreme position to a particularintermediate position between its two extreme positions, termed theorientation intermediate position, which is illustrated in FIG. 9 , inwhich the bell 104 is moved toward the upper face 92 of the mold 88without coming into contact with the upper face 92 of the mold 88. Inthis way at least a lower section of the neck 16 of the preform 12Aremains visible from the outside.

The forming substations 30 are arranged on a common circular trajectorycentered on the central axis “Z2”. During their movement the formingsubstations 30 therefore drive the hollow bodies 12 continuously alongthe forming path of circular arc shape, forming a section of theproduction itinerary 13. The circular trajectory of the formingsubstations 30 is generally divided into four distinct sectors, asrepresented in FIG. 10 .

In a so-called offloading and loading sector “S1” the nozzle 98 is inits retracted extreme position to enable the introduction of a preform12A into the mold 88; for example the preform 12A is positioned by meansof a clamp 89 as illustrated in FIG. 7 . Then in a second sector “S2”directly downstream of the first sector “S1” the nozzle 98 is in itsorientation intermediate position. The clamp 89 is then withdrawn.

In a third or blowing sector “S3” the nozzle 98 occupies its workingextreme position to enable forming of the preform 12A into the finishedcontainer.

On leaving the third sector “S3” the forming substation 30 enters afourth or verification sector “S4” in which the nozzle 98 is in itsorientation intermediate position.

On the leaving the fourth sector “S4” the forming substation 30 returnsdirectly to the first sector “51” in which the nozzle 98 is in itsretracted extreme position to enable extraction of the finishedcontainer and insertion of a new preform 12A to begin a new formingcycle.

As explained in the preamble, in some applications it is necessary toorient the hollow body 12 before carrying out a treatment. For example,a preform 12A heated in accordance with a “preferential” heating profilewill have to be oriented in correspondence with the shape of the mold inthe forming substations 30. To this end, as illustrated in FIG. 11 , itis known to produce at least one angular marker 106 on the neck 16 ofthe preform 12A, as the neck 16 does not undergo any transformation.

The angular marker 106 is for example formed in relief, such as a lug ora notch produced on the neck 16. It may also be a mark produced by localheating or by printing.

An angular offset “α” between the current angular position of thepreform 12A and a reference angular position is for example measured inat least one so-called measurement zone 107 of the production itinerary13. The angular offset “α” is thus an angle that is measured around theprincipal axis “Z1” of the neck 16 of the hollow body 12. When thepreform 12A travels along the heating path the reference angularposition corresponds to the angular position that the preform 12A shouldoccupy around its principal axis “Z1” relative to its support member inorder for the heating profile to coincide with the angular marker 106.When the hollow body 12 travels along the forming path the referenceangular position corresponds to the angular position that the hollowbody 12 should occupy around its principal axis “Z1” relative to themold in order for the angular marker 106 and therefore the heatingprofile to coincide with the shape of the molding cavity 90.

In the context of the present patent the angular offset “α” is heredefined as being oriented, that is to say is between −180° and +180°inclusive, the value 0° corresponding to an angular position of thehollow body 12 corresponding to its reference angular position.

Here the production installation 10 includes a plurality of measurementzones 107. The structure and the functioning of a measurement zone 107will be described generically hereinafter with reference to FIGS. 12 and13 , the description being applicable to all the measurement zones 107of the production installation 10. Thereafter each measurement zone 107will be distinguished by adding to the reference 107 a letter associatedwith each of those measurement zones.

Each measurement zone 107 is equipped with a set of at least one device108 for imaging the neck 16 of the hollow body 12. The imaging device108 is for example a digital video or still camera. The imaging device108 is arranged in such a manner as to capture a digital image in whichthe angular marker 106 on the neck 16 of the hollow body 12 can be seen.There may also be provided means (not represented) for illuminating theneck 16 to guarantee a sharp image of the neck 16 when imaging. Theilluminating means are for example integrated into the imaging device108.

The imaging device 108 is designed automatically to communicate an imageof the neck 16 of the hollow body 12 to an electronic control unit 110in order to be able to execute a step “E1” of measuring the angularoffset “α” of the particular hollow body 12 relative to the referenceangular position in the measurement zone 107 of the production itinerary13.

The measurement step “E1” includes a first phase “E1-1” of capture of atleast one image of the neck 16 of the hollow body 12 on its supportmember by the imaging device 108, which is at a predetermined positionrelative to the production itinerary 13 during imaging. Images of thiskind are for example illustrated in FIGS. 14 and 15 .

The field of view of the imaging device 108 takes the overall form of acone with a principal axis termed the imaging axis “X1”. The imagingdevice 108 is arranged in such a manner that, at the moment of capturingan image, its imaging axis “X1” is oriented toward the neck 16 in such amanner as to capture an image in which the external face 17 of one sideof the neck 16 appears. In the example represented in FIGS. 12 and 13the imaging axis “X1” is arranged globally radially relative to theprincipal axis “Z1” of the neck 16 of the hollow body 12, at the samelevel as the neck 16.

In a variant of the invention that is not represented the imaging axis“X1” has another orientation, for example coaxial with the principalaxis “Z1” of the neck 16 of the hollow body 12.

The imaging device 108 is fixed relative to the floor and its imagingaxis “X1” is oriented toward a particular target point “T”, also fixedrelative to the floor, of the production trajectory. The target point“T” corresponds to the location at which the neck 16 of a hollow body 12is situated in the measurement zone 107.

The imaging device 108 is therefore able to render automatically “on thefly” the image of the neck 16 when it passes the target point “T” on theimaging axis “X1” of the imaging device 108. Accordingly, a single setof at least one imaging device 108 is sufficient to capture an image ofthe neck 16 of each of the hollow bodies 12 passing in single filethrough the measurement zone 107.

If said measurement zone 107 is covered by only one imaging device 108the imaging axis “X1” of which is oriented radially, it is preferablefor the hollow body 12 to be equipped with at least two diametricallyopposite angular markers 106 so as to guarantee that at least one of theangular markers 106 appears in the captured image. In the examplesrepresented in FIGS. 11 to 15 the neck 16 of the hollow body 12 includesfour regularly distributed angular markers 106. If the heating profilefeatures a pattern repeated every 90°, as is the case here, the fourangular markers may be identical.

Alternatively, if the imaging axis “X1” is arranged coaxially with theprincipal axis “Z1” of the neck 16, for example if the angular marker106 is situated on the flange, the neck 16 may include only one angularmarker 106 visible to a single imaging device situated on the principalaxis “Z1” of the neck 16.

Alternatively, the measurement zone 107 includes a set of imagingdevices 108 that are fixed relative to the floor. The imaging axis “X1”of each of the imaging devices 108 is oriented toward the principal axis“Z1” of the neck 16 of a hollow body 12 passing said target point “T”.This enables each of the imaging devices 108 to capture the same neck 16simultaneously from different angles. Accordingly, if the imagingdevices 108 are disposed in such a manner as together to cover the wholeof the cylindrical external face 17 of the neck 16, the neck 16 may beequipped with only one angular marker 106.

The imaging device 108 is able to communicate the captured image of theneck 16 to the electronic unit 110, for example over a wired link or bymeans of an appropriate electromagnetic signal.

During a second processing phase “E1-2” of the measurement step “E1”each image captured by the set of at least one imaging device 108 iscomputer processed to detect the angular position of an angular marker106 visible on the image relative to the reference angular position. Tothis end, the electronic control unit 110 is provided with imageprocessing software that enables identification of the angular marker ormarkers 106 appearing in the image.

Once the position of the angular markers 106 has been identified in theimage, a third phase “E1-3” is triggered during which the angular offset“α” of the hollow body 12 is determined by the electronic control unit110.

As illustrated in FIGS. 14 and 15 , the position of the imaging device108 being fixed, the location, termed the “reference point 106R”, atwhich one of the angular markers 106 in the image should be situated sothat the hollow body 12 occupies its reference angular position, doesnot vary. This reference point 106R is determined before the methodcommences. The electronic control unit 110 calculates the angular offset“α” as a function of the transverse distance between this referencepoint 106R and the current position of the angular marker 106 identifiedin the image. As a function of the current position of the angularmarker 106 relative to the reference point 106R, to the right or to theleft as illustrated in the figures, the electronic unit 110 alsodetermines the direction of the angular offset “α” relative to thereference position.

The production installation 10 represented in FIG. 1 includes at leasttwo measurement zones 107 of this kind equipped with imaging devices 108of this kind.

A first measurement zone 107A is located at the periphery of the notchedwheel 68, just before the preforms 12A are taken up by a turntable 38.

The position of each preform 12A is then corrected individually during acorrection operation as a function of the angular offset “α” measuredfor said preform 12A in a first correction zone 112A downstream of thefirst measurement zone 107A.

The first correction zone 112A is in the passive first section “P1” ofthe heating path, after the preform 12A has been taken up by a turntable38. Thus the orientation devices 84 of the first guide wheel 60 enablecorrect orientation of the turntable 38 in such a manner as to cause theangular position of the crank pin 78 to correspond to a particularangular position of the angular marker 106 of the preform 12A. Thistherefore enables the heating profile of the preform 12A to be caused tocoincide with the angular marker 106.

The second measurement zone 107B is located in the second angular sector“S2” just after where a preform 12A has been installed in a mold 88.Thus the orientation of the preform 12A can be corrected during acorrection operation after its installation in the mold 88 in a secondcorrection zone 112B downstream of the second measurement zone 107B, andhere still in the second angular sector “S2”, in order to make theposition of the angular marker 106 and therefore of the heating profilecorrespond exactly to the shape of the molding cavity 90.

The angular position of the preform 12A is for example corrected bymeans of a rotary nozzle 98 like that described in the document EP 1 261471 B1.

The drive member 114 is mounted to turn about the axis “Z6” relative tothe mold 88 in such a manner as to be able to drive the preform 12A inrotation about its principal axis “Z1” when it occupies its orientationintermediate position. The drive member 114 can be driven in rotation inboth directions in a controlled manner by a motorized rotation drivemeans, for example an electric motor 116. The electric motor 116 iscontrolled automatically by the electronic control unit 110, asillustrated in FIG. 9 .

In a non-limiting manner, in the example represented in the figures thedrive member 114 is constrained to rotate with the bell 104 about theaxis “Z6”, which bell is able to turn about that axis “Z6” relative tothe nozzle 98 to the lower end of which it is fixed. On the other hand,the bell 104 is fastened to the nozzle 98 in the vertical direction. Thedrive member 114 is able to slide vertically relative to this assemblywhen the nozzle 98 is moved from its orientation intermediate positionto its working extreme position.

For example, the drive member 114 is guided as it slides in the bell 104by internal splines of the bell 104 which also guarantee that the bell104 and the drive member 114 are constrained to rotate together aboutthe axis “Z6”.

When the nozzle 98 is in its orientation intermediate positionillustrated in FIG. 9 it can be driven in rotation by the drive device.This drive device essentially comprises the electric motor 116 (togetherwith its control module) that drives the rotation of a meshing gear 118the axis “Z7” of which is parallel to the axis “Z6”. Here the electricmotor 116 is fastened to the nozzle-carrier block 100.

The bell 104 includes an external toothed wheel 120 that meshes with thepinion 54 so that the motor 116 is able to turn the bell 104 and via thelatter the drive member 114.

The operation of the production installation 10 is described next for aparticular preform 12A.

When the production installation 10 is producing containers 12B thepreform 12A is first taken up by a notch of the notched wheel 68. Theangular position of the preform 12A is measured in the first measurementzone 107A. Each turntable 38 is then oriented in the first correctionzone 112B as a function of the angular offset “α” of said preform 12Ameasured in the first measurement zone 107A by the orientation device 84before taking up a preform 12A associated with the take-up point 64 ofthe heating station 20 so as to cause the angular position of theturntable 38 to correspond to the angular position of the preform 12A.The preform 12A is then transported along the heating path 36 by anassociated turntable 38. The body 14 of the preform 12A is heated whilethe preform 12A travels along the active sections “H1, H2” of theheating path 36.

When the preform 12A reaches the transfer point 66 along the productionitinerary 13 it is then taken up by an associated clamp 72 of thetransfer wheel 70 which then transfers the preform 12A to the clamp 89of a transport device. The preform 12A is then installed in the mold 88of an associated forming substation 30 by the clamp 89. The clamps 89are designed to prevent the preform 12A turning about its principal axis“Z1” in order to maintain the preform 12A as close as possible to itsreference angular position.

However, it frequently happens that the preform 12A slips during itstransfer from one transport device to the other downstream of theheating station 20. Moreover, the preform 12A is free to turn about itsprincipal axis “Z1” in the mold 88 until the drive member 114 comes toimmobilize it. To enable this slippage to be corrected the angularoffset “α” of the preform 12A relative to its reference angular positionis measured in the second measurement zone 107B with the aid of theangular marker 106 when the preform 12A comes to be installed in themold 88.

The angular position of the preform 12A is corrected downstream of thesecond measurement zone 107B in the second correction zone 112B as afunction of the angular offset “α” measured for said preform 12A in thesecond measurement zone 107B by means of the rotary nozzle 98.

This kind of production installation 10 enables containers 12B of goodquality to be obtained and guarantees that the heating profile of thepreform 12A corresponds to the shape of the molding cavity 90. However,each operation of correction of the position of the preform 12A has aduration proportional to the value of the angular offset “α” to becorrected in the second correction zone 112B. A result of this is thatthe production rate is limited by the correction operations.

Moreover, it happens that the heating profile is slightly offsetrelative to the position of the angular marker 106. This may be becauseof slippage of the preforms 12A between the first measurement zone 107Aand being taken up a turntable 38. Although errors of this kind aregenerally very small, it remains possible further to improve the qualityof the container 12B produced by minimizing the offset angle “α”. Infact, a tolerance as to the angular offset is permissible, that is tosay if the angular offset is in a particular range, for example between−5° and +5° inclusive, the influence of the angular offset on thequality of the finished container obtained is considered negligible.Accordingly, by reducing the angular offsets obtained for the majorityof the preforms 12A in said tolerance range it is theoretically possibleto avoid most of the preform orientation correction operations. Theinventors have found that, to some degree, it is possible, on average,to reduce the value of the angular offsets “α” found in measurementzones 107 downstream of the first measurement zone 107A. Consideringthat the angular offsets “α” of the various preforms of a string ofpreforms are distributed in accordance with a curve such as a Gaussiancurve, the angular offsets “α” are arranged on either side of the mean“αM”, as illustrated in FIGS. 16 and 17 . The tolerance zone iscross-hatched in FIGS. 16 and 17 .

If the absolute value of said mean “αM” is above a particular threshold,that means that the majority of the preforms have an angular offset thatis not in the tolerance range, as illustrated in FIG. 16 .

The angular offset “α” applied during the subsequent correctionoperation would be reduced overall by choosing to compensate the angularorientation of the upstream preforms in such a manner as to create amean “αM” equal to 0°, as represented in FIG. 17 .

The consequence of this would therefore be to reduce the overallduration of the correction operations. If the majority of the preformshave an angular offset in the tolerance range it is even possible toeliminate totally the correction operation for those preforms.

The invention proposes to enhance the quality of the containers 12B andto increase the production rate thanks to a method for regulation of theangular position of the preforms 12A in the production installation 10.As illustrated in FIG. 18 the method carried out in accordance with theinvention includes:

-   -   the first step “E1” of measuring an angular offset “α” of at        least one particular preform 12A relative to a reference angular        position in a measurement zone 107 of the production itinerary        13; and    -   a second step “E2” of compensation of the angular position of        the subsequent preforms 12A during a compensation operation in a        compensation zone 122 upstream of said measurement zone 107        during which the angular orientation of the subsequent preforms        12A is modified by an updated compensation angle “α1” that is a        function of the angular offset “α” measured for the at least one        particular preform 12A during the first measurement step “E1”        and a current compensation angle “α0” in such a manner as to        reduce the angular offset “α” of the preforms 12A in said        measurement zone 107.

The first measurement step “E1” proceeds in three phases “E1-1, E1-2,and E1-3”, as explained above.

During the first iteration of the method the current compensation angle“α0” is initialized to 0°.

During subsequent iterations the current compensation angle “α0” is setequal to the updated compensation angle “α1” calculated during theimmediately preceding iteration of the method.

Instead of merely correcting the angular position of the hollow bodies12 in a correction zone 112 downstream of each measurement zone 107 theregulation method thus makes it possible to anticipate the angularoffsets “α” to which the subsequent hollow bodies 12 in the single filewill be subjected in the compensation zone 122 in order to reduce thecorrection to be effected in the correction zone 112.

The angular offsets “α” of the hollow bodies 12 in a string of hollowbodies have a random distribution. It is therefore not possible toeliminate completely the angular offset “α” found in each measurementzone. On the other hand, the invention seeks to reduce the mean “αM” ofthe angular offsets found in some measurement zones 107. The mean “αM”of the angular offsets is defined in the conventional manner as beingthe sum of the angular offsets “α” measured for the string of preforms12A divided by the number of hollow bodies 12 in the string.

During the second compensation step “E2” the mean “αM” of the angularoffsets measured for each hollow body 12 in the string of hollow bodies12 is calculated by dividing the sum of the angular offsets by thenumber of hollow bodies 12 during a first phase “E2-1”. The mean “αM” iscalculated by the electronic control unit 110.

To obtain a mean “αM” representative of the distribution of the hollowbodies 12 it is of course possible to spread the isolated angular offsetvalues “α” that depart too much from the mean “αM” established duringthe preceding iteration of the method in order not to take into accountthese angular offset “α” values deemed accidental. In fact theseisolated angular offset values “α” risk falsifying the mean “αM”calculated by the electronic control unit. Then, during a second phase“E2-2”, the updated compensation angle “α1” is calculated as a functionof the calculated mean “αM” and as a function of the currentcompensation angle “α0”. To this end, on each iteration the mean “αM”calculated from the measurements effected during the measurement step“E1” is subtracted from the current compensation angle “α0”.

The value of the current compensation angle “α0” is therefore modifiedduring the second step “E2” if the absolute value of the mean “αM” ofthe angular offsets for each hollow body 12 of a string of at least twoconsecutive particular hollow bodies 12 measured during the firstmeasurement step “E1” is above a particular threshold, for examplegreater than 0°.

Then, during a third phase “E2-3”, the orientation of the subsequenthollow bodies 12 is modified by the updated compensation angle “α1”.

The method is reiterated cyclically to adjust the current compensationangle “α0” on each iteration. In a fourth phase “E2-4”, the compensationangle “α1” updated in the preceding iteration is stored and used againas the current compensation angle “α0” during the next iteration. Thecurrent compensation angle “α0” is therefore modified regularly toapproach the new mean “αM” of 0°.

The mean “αM” is for example calculated for a new string of hollowbodies when the last hollow body 12 of the preceding string has left themeasurement zone 107.

Alternatively, the mean “αM” is calculated on a sliding basis, i.e. anew iteration of the method is undertaken when the preceding iterationhas not finished. This enables the electronic control unit to calculatea sliding mean “αM” of the angular offset. A hollow body 12 cantherefore belong to at least two distinct strings of hollow bodies 12.

There are described hereinafter embodiments of the invention that may beimplemented individually or in a combined manner in the same productioninstallation 10.

In accordance with a first embodiment of the invention, a firstcompensation zone 122A is arranged on the heating path 36 where thepreforms 12A are supported by a turntable 38. The first compensationzone 122A is more particularly in the upstream passage section “P1”.This makes it possible to compensate the position of the preforms 12Abefore heating thereof begins. The first compensation zone 122A is hereformed by the first correction zone 112A. The angular position of thepreforms 12A is compensated by rotation of each turntable 38 in thefirst compensation zone 122A by means of the orientation devices 84.

In accordance with this first embodiment the measurement step “E1” iscarried out in a third measurement zone 107C that is arranged on theheating path 36 downstream of the first compensation zone 122A. Giventhat the orientation of the turntable 38 and therefore of the preform12A is controlled all along the heating path 36, the third measurementzone 107C can be arranged anywhere on the heating path 36 downstream ofthe first compensation zone 122A.

In the example represented in the figures the third measurement zone107C is in the downstream passage section “P3”. Alternatively, the thirdmeasurement zone 107C is in the intermediate passive section “P2”.Arranging the third measurement zone 107C in a passive section “P2, P3”of the heating path 36 makes it possible in particular to avoid exposingthe imaging devices 108 to the heat produced by the heating members 22.

The compensation step “E2” is for example carried out concomitantly withthe operation of correcting the angular position of the preform 12A. Inthis case, for each preform the electronic unit 110 calculates the sum“S” of the correction angle for said preform 12A measured in the firstmeasurement zone 107A and the updated compensation angle “α1” calculatedfrom the measurements carried out on the preceding string of preforms12A in the third measurement zone 107C. Thus the preform 12A is turnedin a single operation by said sum “S” at the level of the firstcompensation zone 122A that also forms the first correction zone 112A.

The compensation method in accordance with this first embodiment of theinvention therefore makes it possible to achieve the best match betweenthe heating profile of each preform 12A and the angular position of theangular marker 106.

In accordance with a second embodiment of the invention there is asecond compensation zone 122B on the heating path 36 where the preforms12A are supported by a turntable 38. The second compensation zone 122Bis more particularly arranged on the downstream passive section “P3”just before the preform 12A is transferred to the first transfer wheel70 and after the heating of the preform 12A has finished. This enablescompensation of the position of the preforms 12A after heating thereofhas finished.

The angular position of the preforms 12A is compensated by rotation ofeach turntable 38 in the second compensation zone 122B by means of oneof the orientation devices 84.

In accordance with this second embodiment the measurement step “E1” iscarried out in a second measurement zone 107B in the forming station 26when the preform 12A is installed in the mold 88 before the formingoperation.

The measurements effected in the second measurement zone 107B thereforeenable individual correction of the angular position of each downstreampreform 12A, but also compensation of the position of the followingpreforms 12A upstream.

The compensation step “E2” is therefore applied to the preforms thatarrive at the end of the heating path 36 before being transferred to theforming station 26. This enables the best match to be achieved betweenthe heating profile of the preforms 12A and the shape of the cavity 90,taking into account the small offsets that are likely to occur duringthe various transfers of preforms 12A from one transport device to thenext and during their installation in the mold 88.

In accordance with a third embodiment of the invention, there is a thirdcompensation zone 122C in the forming station 26, upstream of theforming operation.

The third compensation zone 122C is more particularly downstream of thesecond measurement zone 107B and upstream of the forming operation. Thisenables compensation of the position of the preforms 12A before formingthereof has begun.

The third compensation zone 122C is here arranged on the second angularsector “S2” of the forming path. Here the third compensation zone 122Cis formed by the second correction zone 112B. The angular position ofthe preforms 12A is compensated by rotation of the drive member 114 whenthe preforms 12A are in the third compensation zone 122C.

In accordance with this third embodiment, the measurement step “E1” iscarried out in a fourth measurement zone 107D in the forming station 26downstream of the forming operation. Here the fourth measurement zone107D is in the fourth angular sector “S4”, where the preform 12A hasbeen transformed into the container 12B, and upstream of the point 34 ofextraction from the mold. This kind of arrangement of the fourthmeasurement zone 107D in particular enables verification that theangular position of the preforms 12A has been corrected properly in thesecond correction zone 107B.

The compensation step “E2” is for example carried out concomitantly withthe operation of correcting the angular position of the preform 12A. Inthis case the electronic control unit 110 calculates for each preformthe sum “S” of the correction angle measured for said preform 12A in thesecond measurement zone 107B and the updated compensation angle “α1”calculated from the measurements effected on the preceding string ofpreforms 12A in the fourth measurement zone 107D. Thus the preform 12Ais turned in a single operation by said sum “S” at the level of thethird compensation zone 122C that also forms the second correction zone112B.

The compensation method in accordance with this third embodiment of theinvention therefore enables the best possible match to be achievedbetween the heating profile of each preform 12A and the shape of themolding cavity 90.

The method carried out in accordance with the teachings of the inventionadvantageously enables reduction of the duration of or even eliminationof the correction operations for each of the preforms in the correctionzones 112.

1. A method of regulation of the angular position of hollow bodies (12)in an installation (10) for production of containers (12B) by formingthermoplastic material preforms (12A) in which the hollow bodies (12)are moved in single file along a production itinerary (13) by individualsupport members (38, 88), each of which is equipped with means forcausing the hollow body (12) to turn about its axis (Z1), the methodcomprising: measuring, in a first step (E1), an angular offset (α) of atleast one particular hollow body (12) relative to a reference angularposition in a particular measurement zone (107B, 107C, 107D) of theproduction itinerary (13), compensating, in a second step (E2), theangular position of the subsequent hollow bodies (12) in a compensationzone (112A, 112B, 112C) upstream of said measurement zone (107B, 107C,107D) during which the angular orientation of the subsequent hollowbodies (12) is modified by an updated compensation angle (α1) that is afunction of the angular offset (α) measured for the at least oneparticular hollow body (12) in the first step (E1) and that is afunction of a current compensation angle (α0) in such a manner as toreduce the angular offset (α) of the hollow bodies (12) in saidmeasurement zone (107B, 107C, 107D).
 2. The method as claimed in claim1, wherein the value of the current compensation angle (α0) is modifiedin the second step (E2) if the mean (αM) of the angular offsets of eachhollow body (12) of a string of at least two consecutive particularhollow bodies (12) measured in the first detection step (E1) has anabsolute value above a particular threshold.
 3. The method as claimed inclaim 1, wherein in the second compensation step (E2) the updatedcompensation angle (α1) is calculated by subtracting the mean (αM) ofthe angular offsets of the string of particular preforms (12) from thecurrent compensation angle (α0).
 4. The method as claimed in claim 1,wherein the method is reiterated cyclically, the current compensationangle (α0) being formed by the updated compensation angle (α1) of thepreceding iteration.
 5. The method as claimed in claim 4, wherein,during the first iteration, the current compensation angle (α0) isinitialized to 0°.
 6. The method as claimed in claim 1, wherein theinstallation (10) includes a heating station (20) that is equipped witha transport device (24) provided with support means, termed turntables(38), each of which enables individual transportation of a preform (12A)along a heating path forming a section of the production itinerary (13)and each of which enables the preform (12A) to be caused to turn aboutits axis (Z1), the compensation zone (112A, 112B) being arranged on theheating path while the preforms (12A) are supported by a turntable (38),the compensation of the angular position of the preforms (12A) beingachieved by rotation of each turntable (38) by the updated compensationangle (α1) in the compensation zone (112A, 112B).
 7. The method asclaimed in claim 6, wherein the transport device (24) includes a chain(37) of turntables (38) movement of which is guided by two guide wheels(60, 62), the compensation zone (112A, 112B) being situated in a run ofthe chain (37) that meshes with one of the guide wheels (60).
 8. Themethod as claimed in claim 7, wherein the compensation zone (112A) issituated in a run of the chain (37) that meshes with a guide wheel (60)downstream of a take-up point (64) at which the preforms (12A) aretransferred from an upstream transport device (68) and before thebeginning of the heating of the preform (12A).
 9. The method as claimedin claim 8, wherein the measurement zone (107C) is situated in theheating station (20) in a run of the chain (37) that meshes with a guidewheel (60) upstream of a transfer point (66) at which the preforms (12A)are transferred to a downstream transport device (70) in the directionof a forming station (26) and after the heating of the preform (12) hasbeen finished.
 10. The method as claimed in claim 1, wherein theproduction installation (10) includes a forming station (26) in whicheach hollow body (12) is moved along a forming path forming a section ofthe production itinerary (13), each preform (12A) undergoing anoperation of forming it into a final container (12B) along the formingpath.
 11. The method as claimed in claim 7, wherein the compensationzone (112B) is situated in a run of the chain (37) that meshes with aguide wheel (60) upstream of a transfer point (66) at which the preforms(12A) are transferred to a downstream transport device (70) in thedirection of a forming station (26) and after the heating of the preform(12A) has been finished.
 12. The method as claimed in claim 11, wherein:the production installation (10) includes a forming station (26) inwhich each hollow body (12) is moved along a forming path forming asection of the production itinerary (13), each preform (12A) undergoingan operation of forming it into a final container (12B) along theforming path, and the measurement zone (107B) is situated in the formingstation (26) downstream of the heating station (20) before the formingoperation is begun.
 13. The method as claimed in claim 10, wherein thecompensation zone (112C) is situated along the forming path before theforming operation is begun.
 14. The method as claimed in claim 13,wherein the measurement zone (107B) is situated in the forming station(26) along the forming path after the forming operation has beenfinished.
 15. The method as claimed in claim 2, wherein in the secondstep (E2) the updated compensation angle (α1) is calculated bysubtracting the mean (αM) of the angular offsets of the string ofparticular preforms (12) from the current compensation angle (α0). 16.The method as claimed in claim 2, wherein the method is reiteratedcyclically, the current compensation angle (α0) being formed by theupdated compensation angle (α1) of the preceding iteration.
 17. Themethod as claimed in claim 3, wherein the method is reiteratedcyclically, the current compensation angle (α0) being formed by theupdated compensation angle (α1) of the preceding iteration.
 18. Themethod as claimed in claim 2, wherein the installation (10) includes aheating station (20) that is equipped with a transport device (24)provided with support means, termed turntables (38), each of whichenables individual transportation of a preform (12A) along a heatingpath forming a section of the production itinerary (13) and each ofwhich enables the preform (12A) to be caused to turn about its axis(Z1), the compensation zone (112A, 112B) being arranged on the heatingpath while the preforms (12A) are supported by a turntable (38), thecompensation of the angular position of the preforms (12A) beingachieved by rotation of each turntable (38) by the updated compensationangle (α1) in the compensation zone (112A, 112B).
 19. The method asclaimed in claim 3, wherein the installation (10) includes a heatingstation (20) that is equipped with a transport device (24) provided withsupport means, termed turntables (38), each of which enables individualtransportation of a preform (12A) along a heating path forming a sectionof the production itinerary (13) and each of which enables the preform(12A) to be caused to turn about its axis (Z1), the compensation zone(112A, 112B) being arranged on the heating path while the preforms (12A)are supported by a turntable (38), the compensation of the angularposition of the preforms (12A) being achieved by rotation of eachturntable (38) by the updated compensation angle (α1) in thecompensation zone (112A, 112B).
 20. The method as claimed in claim 2,wherein the production installation (10) includes a forming station (26)in which each hollow body (12) is moved along a forming path forming asection of the production itinerary (13), each preform (12A) undergoingan operation of forming it into a final container (12B) along theforming path.